This invention related to a method for mounting components and an apparatus therefor and more particularly to an improved arrangement that permits the accurate picking up and mounting of components and a method for performing such operations.
There are a wide variety of applications wherein components are picked up from a feed section where they are delivered and moved to and placed at an accurate location. A wide variety of devices are employed for actually picking up the components. Frequently such pick up devices employ vacuum nozzles for picking up the components.
A specific application for this type of apparatus and method is in the making of printed circuit boards. With such printed circuit boards, it is common to employ a device called a "chip mounter" that picks up small components such as integrated circuits, resistors or capacitors at a feed section and places them on a printed circuit board. Vacuum nozzles are frequently employed as the pick up devices.
In order to render such devices more versatile, it has been proposed to provide an arrangement wherein the form and type of pick up nozzle employed may be readily changed so as to suit particular components. This nozzle changing may be done either manually or automatically.
The criticality for accurately mounting such components is readily apparent. However, in the process of mounting the nozzle, mistakes may be made even if the apparatus functions automatically and these mistakes can result in inaccurate mounting of the components and other problems. For example the interchangeable pick up devices may by their very nature have different lengths or different configurations from each other. Frequently, however, it is necessary or desirable to perform a further operation on the component once it has been picked up and this operation should be performed at an accurate location. For example, it is a practice to employ an optical sensor for sensing certain characteristics of the component being picked up. However, if the pick up device has different configuration, the picked up component may not be positioned in the proper location for the sensing operation.
It is, therefor, an object of this invention to provide an improved method and apparatus embodying pick up devices wherein the pick up device is sensed so as to provide a reference location where components will be positioned by the pick up device for performing a further operation on the component.
One of the operations that may be performed on the component once it is picked up by the pick up device is a sensing operation that will sense the orientation of the component relative to the pick up device so as to make a corresponding correction in the movement of the component to the mounting position so that it will correctly mounted. One type of device for such sensing involves rotation of the component in front of an optical sensor. However, if the pick up device is mounted in such a way that its axis is displaced from the fixed rotational axis of the apparatus, then the sensing and subsequent calculation of a correction factor may be incorrect.
It is, therefor, a still further object of this invention to provide an improved method and apparatus for determining the rotational axis of a replaceable pick up device once the pick up device has been installed in the apparatus.